A recent study conducted by researchers at the University of Milan is offering a new and exciting theory on the impact that sleep deprivation has on the human brain. The research, which was recently profiled in Science News by Laura Sanders and published in the journal Cerebral Cortex, was led by Marcello Massimini, whose team conducted experiments on six study participants who were tested both before and after a night of sleep deprivation. Their results are leading sleep experts to the belief that sleep deprivation leaves our brains in a state of overstimulation that can lead to a level of hyper-reactivity that may explain the prevalence of seizures and hallucinations in those who have been kept awake for too long. The study involved measuring the brain responses of participants both before and after a night of sleep deprivation. The responses were measured utilizing a powerful burst of magnetic current that was administered via electrodes placed on the scalp, and then determining the amount of electrical response that was elicited from that magnetic current when the participants were well rested versus not having had adequate restorative sleep. Their results showed that the electrical responses elicited were far stronger in those without sleep then those who had gotten enough sleep, pointing to a sort of overheating of the brain that happens when adequate sleep isn’t gotten. The study’s results are in keeping with recent theories about the purpose of sleep: these theories have posited that sleep sweeps the brain of extraneous information that is collected during the day, keeping connections that are necessary and getting rid of what we don’t need. The hyper-reactivity of the brain in the face of inadequate sleep is an indication that this cleaning out has not happened, and that the excessive number of connections that have been formed between the brain’s nerve cells acts to overburden the brain, leaving it overly excitable. Overly stimulated brain function can lead to a number of negative physical and emotional responses, including an increased incidence of seizures, hallucinations and – interestingly – a reversal of signs of depression. The information gathered in the study can be utilized in a number of different ways. First, it makes clear and solidifies the notion that the brain is cleansing itself of clutter whenever it goes to sleep, emphasizing the physiological need for this important function. It also may aid those studying the treatment of depression, as understanding why and how sleep deprivation and its ensuing overstimulation of the brain’s nerve cells positively impacts the symptoms of depression. A better understanding of this phenomenon may lead to improved medications and treatments for those suffering from both sleep disorders and a number of mental illnesses, and will add to our understanding of the relationship between sleep deprivation and mood.